High tensile strength, synthetic rope has been developed and used in towing and winching applications due to its lighter weight than steel cable and its higher strength under tension than steel cable of the same diameter. In fact, ropes woven of high-modulus polyethylene (HMPE) (e.g., Plasma, Spectra, Dyneema and Amsteel) are rated for many high load and tension applications including towing, winching, and mooring. Among other characteristics, HMPE rope has a high resistance to abrasion and ultraviolet degradation and a low percentage of elongation. A synthetic winch line that is unsheathed will be more susceptible to chafing. It must be kept free of sand and grit that can work their way into and between the strands of the rope and cause internal abrasion. The winch line should further be covered during the day so that UV rays don't damage the rope.
It is also more vulnerable to heat, whether it comes from chafing or the internal drum brake. Depending upon the formulation of the synthetic rope, temperatures between 150 and 450 degrees Fahrenheit can cause the rope to lose strength. These temperatures can be reached through heat transfer of the winch brake through the winch drum. If the rope repeatedly reaches these high temperatures, “heat aging” occurs, which extremely weakens the rope. If the rope reaches a melting temperature between 290 and 900 degrees (depending on the formulation of the rope), the rope can melt. Thus, it is important to allow the brake to cool off as necessary when in use. However, waiting during these necessary cooling periods can significantly delay the operations needed to be performed by the winch and winch line.
Synthetic rope winch lines are often formed with eyes on the free end for attaching to rigging connectors such as shackles or hooks. The eyes are generally formed by slicing the synthetic rope into itself to form a loop or eye. They eyes are also often reinforced with a metal thimble that lines the inner wall of the rope forming the eye opening. The thimble provides abrasion resistance and helps maintain the form of the eye when placed under tension in order to avoid failure of the rope. Bends in the rope at too small a radius can significantly compromise the strength of the rope and can lead to failure. Thimbles can also act as a stopper or block to prevent the winch line from pulling through the fairlead when the winch line is retracted and wraps around the winch drum. However, as thimbles are typically metal, they can damage the fairlead if pulled against it tightly or by banging against the fairlead during transit if not pulled tightly against it. Such impacts can cause abrasions to, gouges in, or burs on to the fairlead through which the winch line rope travels. These abrasive features can rub or cut into the winch line as it travels through the fairlead, thus compromising the integrity of the winch line.
Presently, winch lines, both steel cable and synthetic rope, are typically attached to the winch drum at a single point by a either a set screw connecting a ferrule on the end of the winch line against the drum. Alternatively, the end of a synthetic winch line can be inserted into a hole in the drum, which creates a binding connection as the rope is bent and wrapped around the drum away from the hole. These configurations can lead to failure of the winch line if too much line is played out off of the drum. If winch line is not wrapped around the winch drum enough times past the connection point to maintain a strong grip or bite between the winch line and the drum, the tension on the winch line can easily pull the winch line out from under the set screw or out of the hole and result in failure.
The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded subject matter by which the scope of the invention as defined in the claims is to be bound.